Messages in this thread | | | Date | Fri, 22 Jan 1999 17:20:27 +0000 (GMT) | From | Bill Melotti <> | Subject | RAMDISK Bug - 2.0.36 kernel |
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Hi
Can anyone offer any suggestions on a possible RAMDISK bug I have seen.
I wish to boot a system from a flash IDE drive into a 16Meg RAMDISK on a system with 32 Meg installed. I have modified drivers/block/rd.c and commented out the line that checks for a floppy as the root dev, this allows me to at least load a compressed filesystem image from an HD into RAMDISK.
The system I have uses about 11 meg of the 16. You would imagine I have a little less than 16Meg available for application use. Actually I have a few processes running from boot and free reports only about 6Meg left.
I tried running some programs that would allocate memory until failure to confirm what was really available (because I though 6 was a little low)
I wrote a program that would malloc single large blocks. With this I can malloc 23 Meg before failure. (malloc returns NULL)
Thinking there was a problem, I changed this to use calloc instead. If I tried to calloc more than 10 Meg, the machine locked up. Between 6 and 10 it would usually keep going for a while, but lock up later. I tried running these programs as nobody rather than root. Same result. If I were running any other programs (eg 'top') in another session, this would usually bomb with a bus error at the same time. The callocing app might also bomb with a bus error before the machine locked. I am doing this stuff over a telnet session, I haven't tried it on a console.
It is as if the RAMDISK code as not marked the buffers it uses as unavailable for app code. I looked through the code and see it sets the BH_Protected flag in the file buffer structs. However I also see that there are 2 or 3 places (fs/buffers.c and somewhere in ext2 hierarchy) where these can be cleared.
Can anyone offer any help/comments/suggestions ?
Many thanks
Bill Melotti Cognito Ltd UK
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